A continuous drum blasting machine is known from German Pat. No. 109,648, wherein a cylindrical drum rotates about an axis inclined with respect to the horizontal, the interior of the drum having several longitudinally displaced blast nozzles for the purpose of cleaning and de-burring of workpieces, particularly of cast pieces. Since the workpieces are carried partly by the rotating inside wall of the drum and then dropped back again into the lower area of the drum, and on many occasions slide down along the slanting interior surface of the drum, a completely uncontrollable and uneven movement of passage through the drum and turning of the workpieces results. In the case of variable kinds of workpieces, this leads particularly to a greatly fluctuating throughput with great variation in the amount of blasting to which the workpieces are subjected. If it is desired to efficiently arrange blast wheels within the drum, the diameter of the drum must be selected very large, as a result of which the production costs and the size of the installation, as well as the revolving behavior of the machines, are adversely influenced.
An attempt has been made to achieve a more even conveyance of the workpieces by arrangement of spirals on the inside wall of the drum in the case of horizontal cylindrical drums as shown in U.S. Pat. No. 3,821,866. However, it developed that the workpieces tumble and do not glide along the wall of the drum and therefore the desired uniform conveyance effect does not result. In addition, the sides of individual workpieces tend to be shielded or covered up by the flanks of the spiral with the result that those sides are poorly blasted or not blasted at all. Furthermore, the flanks of the spirals are subjected to considerable wear.